Vitamin D, Should We Take It?

Caveman Doctor recently received an email about vitamin D: whether it should be taken it and what type.  After Caveman Doctor finished reading about what a vitamin was, he did a couple experiments where he tried a couple different brands.  They all tasted badly.  He then tried not chewing them before swallowing.  While he isn’t sure why anyone would ever need to take a vitamin since they didn’t exist in his time, he was very impressed with what he read on the “internet.”  He even takes it himself during certain times throughout the year.


Cavemen didn’t take vitamin D, why should I?

Cavemen got sun.  They migrated to warm places.  They were outside most of the time.  Vitamin D is naturally produced within the body (endogenously) when our skin comes into contact with the sun’s rays.  Caveman Doctor received significant sun exposure in his time.  He rarely did anything exclusively inside.  When hunting all day, he was getting sunlight.  When eating meals outside, he was getting sunlight.  He did not have sunscreen and spent most, and nearly all, of his time outdoors.

Cholecalciferol (D3) is the natural form synthesized within the body in conjunction with UV exposure from the sun.  As you will read below, it has many physiologic properties.  Our body even has a feedback loop so it will stop production if our vitamin D levels get too high from long periods of sun exposure.


Are there health benefits of vitamin D?

First off, vitamin D is actually no vitamin at all.  It is a hormone with many important jobs as it circulates throughout the body.  It promotes healthy bone growth and can protect us from osteoporosis and other bone disorders.  It binds to and activates B and T cells, which are our immune system’s troops to fight infection, which enhances our body’s defenses.  This had led to its use in the treatment of tuberculosis, influenza, and bacterial and viral infections1.  It also regulates genes that control cell proliferation and apoptosis (programmed death), as well as cellular differentiation – all processes vital in the formation and progression of cancer.

Low levels of vitamin D have been associated with increased cancer incidence and mortality in men, setting off a plethora of studies connecting the two2It has been shown to reduce cancer risk for postmenopausal women in a randomized trial – the gold standard of medicine (half of the patients got it, half did not)3.  In a petri dish, vitamin D3 treatment of prostate cancer cells blocked the proliferation of the cancer cells4.  Another study showed no benefit in terms of colorectal cancer, however, it was highly criticized due to the fact that patients only received a tiny dose of 400 IU of D35.  Another study showed that colorectal cancer rates were lower with the higher the amount of vitamin D that was taken6A meta-analysis reviewing 9 studies and 1,000,000 patients revealed that the higher the vitamin D intake and vitamin D blood levels (25[OH]D), the lower risk of cancer7.  Also, interestingly, colon cancer rates are highest in areas of the US where sunlight exposure is the least8.  This is only observational and proves nothing, but interesting nonetheless.  A similar study looked at 111 countries throughout the world and found that higher rates of sun exposure and UV rays (UVB) were independently associated with significantly lower rates of lung cancer9.

However, while breast, colon, ovarian, and prostate cancer were all shown to be associated with decreased sun exposure, non-melanoma skin cancer (basal cell and squamous cell cancers) were also associated with sun exposure10.  Though, basal and squamous cell carcinomas of the skin are rarely lethal and can often be managed with local excision, while those other listed cancers are deadly.  Also, of note, preventive strategies of sun avoidance have yet to show proven benefit in decreasing these skin lesions11.

In fact, vitamin D is one of the few vitamins and supplements Caveman Doctor takes, as he lives in a seasonal climate and often spends much of his time in the hospital, sheltered from the sun.  Caveman Doctor is extremely stubborn and hates when he or patients take pills or unnecessary medicine, however, thus far Vitamin D has stood the test of time.


Does it matter which type of vitamin D?

Yes.  While information on vitamins is generally lacking due to limited studies and rare head-to-head randomized studies, vitamin D is one of the few vitamins where some data exists.  A Cochran Analysis, which is a study looking at all the available randomized trials on vitamin D, looked at 50 trials and over 94,000 participants (mostly elderly women) on vitamin D supplementation12.  The results showed that supplementation with Vitamin D3 (colecalciferol) reduced mortality, while vitamin D2 (ergocalciferol) did not.

Why the difference?  One possibility is the source of the Vitamin D.  Vitamin D2 is a synthesized version, derived from a cell membrane produced by fungi and plankton when they are exposed to UV light.  It is not produced by humans and likely does not affect production of 25(OH)D, our serum version of vitamin D.  As you read above, vitamin D3 is the naturally occurring form within our body and some studies reveal it to be more potent (greater bioefficacy) than D213.  Other studies question these findings14.  Regardless, when compared head-to-head, the results are conclusive, vitamin D3 is the healthier form, cost is basically the same, and there is no reason to risk taking D2.


Take the Purest Form

Finally, many supplements and vitamins contain fillers and other chemicals.  I take vitamin D for vitamin D, not soybean oil, safflower oil, and corn oil – all vegetable oils often added to vitamins and supplements.  As you will read in another post, I would never purposefully consume vegetable oils.  Gelatin and even glycerin are often used as casings for the vitamins, but besides these additives, the least amount of other ingredients the better.  That being said, it seems that most or all of them have some additives.  Aim for the least.

A great part of vitamin D is the price.  It is dirt cheap in pill form, unlike most medications out there that are emptying patients’ pockets and filling those of the drug companies.  Better yet, it is free in sunlight form (not to mention the other benefits of getting out of the house or office for a least a small amount if time).


In Conclusion

  1. In periods where sunlight exposure is limited (winter months, heavy work periods, etc) men can safely take15 4,000 IU per day and women 2,000 IU per day (though higher if deficient and attempting to drastically raise levels).  Small men or large women can hedge toward 3,000 IU per day
  2. When possible get moderate sun exposure.  Generally 20 minutes per day is adequate.
  3. Avoid getting sunburn as this causes trauma, inflammation, and damage to the skin.  Know your limits.
  4. If you put sunscreen on during these 20 minutes, you are likely blocking some or much of the Vitamin D-producing benefit of the sun (with questionable benefit and possibly a false sense of security).

Be informed and be healthy!




1.         Yamshchikov AV, Desai NS, Blumberg HM, Ziegler TR, Tangpricha V. Vitamin D for treatment and prevention of infectious diseases: a systematic review of randomized controlled trials. Endocr Pract. Jul-Aug 2009;15(5):438-449.

2.         Giovannucci E, Liu Y, Rimm EB, et al. Prospective Study of Predictors of Vitamin D Status and Cancer Incidence and Mortality in Men. Journal of the National Cancer Institute. 5 April 2006 2006;98(7):451-459.

3.         Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr. Jun 2007;85(6):1586-1591.

4.         Skowronski RJ, Peehl DM, Feldman D. Vitamin D and prostate cancer: 1,25 dihydroxyvitamin D3 receptors and actions in human prostate cancer cell lines. Endocrinology. May 1993;132(5):1952-1960.

5.         Wactawski-Wende J, Kotchen JM, Anderson GL, et al. Calcium plus Vitamin D Supplementation and the Risk of Colorectal Cancer. New England Journal of Medicine. 2006;354(7):684-696.

6.         Garland C, Barrett-Connor E, Rossof A, Shekelle R, Criqui M, Paul O. DIETARY VITAMIN D AND CALCIUM AND RISK OF COLORECTAL CANCER: A 19-YEAR PROSPECTIVE STUDY IN MEN. The Lancet. 1985;325(8424):307-309.

7.         Ma Y, Zhang P, Wang F, Yang J, Liu Z, Qin H. Association between vitamin D and risk of colorectal cancer: a systematic review of prospective studies. J Clin Oncol. Oct 1 2011;29(28):3775-3782.

8.         Ford ES, Zhao G, Tsai J, Li C. Vitamin D and all-cause mortality among adults in USA: findings from the National Health and Nutrition Examination Survey Linked Mortality Study. International Journal of Epidemiology. August 1, 2011 2011;40(4):998-1005.

9.         Mohr SB, Garland CF, Gorham ED, Grant WB, Garland FC. Could ultraviolet B irradiance and vitamin D be associated with lower incidence rates of lung cancer? Journal of Epidemiology and Community Health. January 1, 2008 2008;62(1):69-74.

10.       Freedman DM, Dosemeci M, McGlynn K. Sunlight and mortality from breast, ovarian, colon, prostate, and non-melanoma skin cancer: a composite death certificate based case-control study. Occup Environ Med. Apr 2002;59(4):257-262.

11.       Madan V, Lear JT, Szeimies R-M. Non-melanoma skin cancer. The Lancet.375(9715):673-685.

12.       Bjelakovic G, Gluud LL, Nikolova D, et al. Vitamin D supplementation for prevention of mortality in adults. Cochrane Database Syst Rev. 2011(7):CD007470.

13.       Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr. Oct 2006;84(4):694-697.

14.       Holick MF, Biancuzzo RM, Chen TC, et al. Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. J Clin Endocrinol Metab. Mar 2008;93(3):677-681.

15.       Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr. May 1999;69(5):842-856.

16.       Garland CF. More on preventing skin cancer. Bmj. 2003-11-20 00:00:00 2003;327(7425):1228.



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  3. Kim

    How do you feel about D3 in liquid form in extra virgin olive oil? I read that the liquid absorbs better than pills and olive oil seems to be the exception when it comes to vegetable oils.

    1. cavemandoctor (Post author)

      I am taking that same source right now from Nature Gold (I think – I’m on the road).

    2. Allison

      I’ve got a great D supplement. Contact me directly for more information.

      Vitamin D3 (As Cholecalciferol) 2000 IU
      Vitamin D (As Menaquinione MK4 & MK7) 30 pg

      This Vitamin D supplement is made with cholecalciferol (vitamin D3), which research suggests is better
      than competing forms at raising levels of vitamin D in the blood. Cholecalciferol can be acquired through diet
      and exposure to sunlight. Light-induced synthesis occurs in the skin when ultraviolet light reacts with a form
      of cholesterol, converting it to cholecalciferol. This molecule is then altered by the liver and kidneys to form
      the physiologically active vitamin D. Several forms have vitamin D or potential vitamin D activity. The most
      important forms are vitamin D2 and vitamin D3. The latter is the form normally found in humans and is also
      the form used in manufacturing this Vitamin D supplement.

      Even when the winter months are behind us, it doesn’t mean your body needs less of a good thing. Every cell
      in your body needs vitamin D to function properly. This Vitamin D supplement is a safe and easy way to
      get 2,000 IU of maximum-strength vitamin D enhanced with 30 µg of vitamin K.*


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